Of course, there is a bit more to making a cross toolchain, but as stated at the beginning of this article, only the unique differences for Funtoo are shown here.
You should find nearly all the rest you need to know at https://www.gentoo.org/proj/en/base/embedded/handbook/
cross-compiler.xml?style=printable. Only the top 1/4 page is needed.
One note, at the current time (11-1-14) you need to preface your crossdev command line statement with USE="-sanitize". This is a known bug (not Funtoo specific) that will soon be fixed in crossdev. You will find -sanitize in the package.use files, but you still must do it on the command line, else gcc will fail. For example the following command line was successful for me today